The invention relates to a method for preparing a solid composite material to be implanted in a human or animal biological medium, especially as a bone or dental substitute; a resulting material; an implant comprising such a material and a kit for carrying out said method extemporaneously.
In all the following specification of the present application, the term "implant" indicates any device, apparatus, mechanism, piece or group of pieces, of natural or artificial origin, organic or inorganic, in a solid condition, biocompatible and implantable in the human or animal body, excluding the fluid, pasty or divided compositions.
As examples of implants, bone, dental or maxillo-facial protheses, as well as filling, stopping or interface inserts, may be mentioned.
The use of porous ceramics having interconnected pores as an implantable solid material for bone substitutes was already described (see for ex ample EP-A-O 360 244 a nd "Osseointegration of macroporous calcium phosphate ceramic s having a different chemical composition", Frayssinet et al., Biomaterials 1993, Vol. 14, No 6, p 423-429). Due to their very macroporosity as such, the implantable biocompatible porous solid matrices such as ceramics, and more specifically the matrices having interconnected pores, are advantageous in that they increase the interchange surface area with the biological medium, are bioresorbable, promote the revascularization of the tissues and have excellent osteoconductive properties. Moreover, growth agents may be deposited into the pores by means of precipitation.
Such porous ceramics, however, are brittle and friable and are not able to be easily shaped by the practitioner during an operation. Further, the fixation of screws or pins in such ceramics is likewise impossible. Accordingly, the practical use of such ceramics is currently limited to the rare cases when it is certain, beforehand, that the material neither will have to be dressed again and adjusted extemporaneously, nor to support fixation screws.
Further, porous ceramics have a poor mechanical strength (2 to 4 MPa in compression) , inadequate in a number of applications, for example when a renewed load of the application site is necessary before healing is completed.
Besides, implantable, biocompatible, phosphocalcic hydraulic cements are known (for example EP-A-0 639 366), i.e. hardenable pasty or fluid compositions allowing the realization of prosthetic assemblies or fillings during orthopaedic surgical operations. Although easily moldable by the practitioner, such cements cannot be used for realizing solid implants such as bone protheses having a predetermined general shape, which must resist from the moment of the implantation high stresses and/or wherein screws have to be screwed for the attachment of other elements or members. Accordingly, such cements are used only for cementing implants or members on each other, or sometimes as a filling material in sites which are not liable to undergo severe stresses.